1. Field of the Invention
This invention pertains to a service distribution device which distributes service requests from clients among several servers using a network.
2. Description of the Related Art
In recent years, network services have grown in scale and become more complicated, resulting in a demand for high performance servers. The response has been to distribute a service among several servers, using load distribution technology to realize the performance of multiple servers. To realize the performance of multiple servers, a technology for distributing and balancing services according to the processing performance of the individual servers has been sought.
A distribution method is known that determines the response time of the servers and distributes the service to the server having the shortest response time. Also known is a distribution method that predicts, based on the current response time and the response time when a server is overloaded (when there are processing errors) or when the processing load is high (when the service time increases as waits are generated), which server will be least likely to become overloaded or have a high processing load.
Nevertheless, the conventional technology has several problems. One problem is that when there is a difference in processing capacity among the servers, the load tends to go to the fastest server. Also, when there is a difference in the service processing content, the server load predictions may be incorrect and the load may not be balanced. Another problem is that because it is difficult for the user to set a threshold value, every server has to become overloaded or placed in a high load state at least once or a threshold value cannot be determined and distribution becomes impossible. In order to intentionally determine the threshold value, it is necessary to halt the service and run a benchmark or other test.